The present invention concerns a drive unit for a motor vehicle having an engine, a hydrodynamic retarder and a transmission.
In vehicle drive systems, retarders play an ever more important role. Used in the motor vehicle, and also in systems with greatly changing operation, the retarder is turned on and off by charging the impeller-equipped working circuit with an operating medium and by draining it. Examples of suitable operating mediums are oil and water. When the retarder is engaged in braking action, the operating medium heats up. The heat must be removed by a radiator.
Drive units of motor vehicles normally include additional units that require cooling. The engine, the mechanical brakes, the clutch and the transmission are examples of such additional units. These other units may also feature a cooling circuit. It is known to operate the retarder in an automotive drive system with water which also serves as a coolant. In nonbraking operation, the retarder can be used selectively as a pump, and the operating medium of the retarder may, at the same time, serve as cooling medium for other units of the drive assembly.
DE 195 09 417 A1 shows and describes a drive train for a motor vehicle comprising an engine, a transmission and a retarder. The retarder is integrated in the end section of the transmission housing.
The objective underlying the present invention is to improve such a drive train to economize and simplify the manufacture and assembly of retarder and transmission to produce a less expensive retarder and transmission.